The present invention relates to a magneto-resistance effect type head for detecting an intensity of a magnetic field based on a resistance change corresponding to this intensity and an information reproducing apparatus for reproducing information stored on a storage medium.
Recently, with prevalence of computers in the society, an enormous amount of information is handled daily. To store such information is there available a magnetic disk. The magnetic disk has its surface made of a magnetic material, which is divided into many minute 1-bit segments, according to a magnetization direction of each 1-bit segment the information can be stored at a high storage density. To reproduce such information is there available a hard disk drive, which has a magnetic head for detecting an intensity of a magnetic field generated by the magnetization of the magnetic disk. The magnetic head sequentially reads out a magnetization direction of each 1-bit segment of the magnetic disk to generate an electric reproduced signal corresponding to the magnetization direction, thus reproducing the information born by use of that magnetization.
The recording density of the information stored on a magnetic disk has been increasing year by year with an accompanying decrease in the area occupied by each 1-bit segment of the magnetic disk. To detect a direction of the magnetization of such a small-area 1-bit segment, it is necessary to use a reproducing magnetic head with a high sensitivity.
As the high-sensitivity reproducing magnetic head is available a magneto-resistance effect type head (hereinafter called MR head) utilizing the magneto-resistance effect of a changing resistance in correspondence with an external magnetic field, especially a spin-valve type MR head well known for its very high sensitivity. This spin-valve type MR head is comprised of a multi-layer film including a soft-magnetism free-magnetic layer which changes in orientation of magnetization corresponding to an external magnetic field, in which the resistance changes greatly with a change in that magnetization orientation. This spin-valve type MR head comes in contact or in near contact with each 1-bit segment of the magnetic disk at a read-out portion of its surface perpendicular to the multi-layer film to thereby detect a magnetic field generated by magnetization of that 1-bit segment, thus generating an electric reproduced signal based on a change in resistance corresponding to that magnetic field.
The free-magnetic layer of the multi-layer film is liable to have a magnetic domain wall occurring at the end, so that if this magnetic domain wall moves due to a change in an external magnetic field, the reproduced signal contains Barkhausen noise. To inhibit the generation of the Barkhausen noise, a magnetic domain-wall control layer made of, e.g., a hard-magnetism ferromagnetic material is arranged as one layer of the multi-layer film, so that the free magnetic layer has the magnetic domain wall fixed due to a static magnetic field and switched connection brought about by that magnetic domain-wall control layer. Although this magnetic domain-wall control layer is preferably thinned in order to realize a small read-out portion fitted to reproduction of information recorded on a magnetic disk at a high recording density, it needs to have a predetermined thickness in order to control the electric domain wall in a stable manner by applying a strong static magnetic field on the free magnetic layer. By utilizing switched connection brought about when the free magnetic layer and the magnetic domain-wall control layer come in direction contact with each other, however, it is possible to compensate for a decrease in the intensity of the static magnetic field caused by the thinning of the layer.
Conventionally, such a spin-valve type MR head with a construction having a very small junction called an abutted junction has been well known that the magnetic domain-wall control layer attached to a tapered layer cross section of the free magnetic layer. That junction has switched connection occurring thereat but can hardly preserve stable connection because it has a small junction area.
Therefore, such a construction has been worked out that is of a so-called vertical-bias underlay type, in which part of the free magnetic layer is stacked on, as covering, the magnetic domain-wall control layer directly or with an underlying layer therebetween. By this construction, when the free magnetic layer is directly stacked on the magnetic domain-wall control layer, an area of the junction between these layers is very large as compared to a junction area of the abutted junction, so that stable switched connection can be preserved always, thus effectively inhibiting the occurrence of the Barkhausen noise.
Generally, however, preferably the free magnetic layer is formed on a predetermined non-magnetic underlying layer so that the existence of the underlying layer assures good crystallinity of the free magnetic layer. Good crystallinity improves the soft-magnetization properties of the free magnetic layer, which in turn improves the sensitivity of the spin-valve type MR head.
The spin-valve type MR head having a vertical-bias underlay type construction in which this free magnetic layer is formed on one pair of magnetic domain-wall control layers with a non-magnetic underlying layer therebetween is disclosed in Japan Patent Publication Hei 10-312515. Although, in this spin-valve type MR head, the non-magnetic underlying layer weakens or eliminates the switched connection between the magnetic domain-wall control layer and the free magnetic layer, this weakness in switched connection can be compensated for by enhancing, in adjustment, the intensity of a static magnetic field of the magnetic domain-wall control layer given to the free magnetic layer.
However, the spin-valve type MR head that has such a vertical-bias underlay type construction that the free magnetic layer is formed on the non-magnetic underlying layer cannot effectuate a feature of the structure held by the spin-valve type MR head that stable switched connection can be obtained by direct junction of the magnetic domain-wall control layer and the free magnetic layer. Therefore, there is desired such a spin-valve type MR head that has good crystallinity as well as high sensitivity, and effectively inhibits the occurrence of the Barkhausen noise by utilizing the feature of the vertical-bias underlay type construction of obtaining stable switched connection between the free magnetic layer and the magnetic domain-wall control layer.
In view of the above, it is an object of the present invention to provide a spin-valve type magneto-resistance effect type head and information reproducing apparatus which can well reproduce information recorded on a recording medium at a high recording density while inhibiting occurrence of the Barkhausen noise.
To the above-mentioned end, a first magneto-resistance effect type head according to the present invention includes:
a magneto-resistance effect element exhibiting a change in resistance in correspondence with an intensity of an external magnetic field, to detect the magnitude of the resistance of the magneto-resistance effect element, thus detecting the intensity of the magnetic field, in such a configuration that:
the magneto-resistance effect element is comprised of a multi-layer film including a free magnetic layer which has a magnetization direction changing in correspondence with the external magnetic field, the magneto-resistance effect type head having:
an insulating layer made of an insulating material;
a non-magnetic underlying layer formed on the insulating layer; and
one pair of magnetic domain-wall control layers formed on the underlying layer in its in-face direction with a predetermined spacing therebetween, for controlling the movement of the magnetic domain wall of the free magnetic layer,
in which the free magnetic layer is formed in such a manner as to have its both ends directly stacked on the pair of the magnetic domain-wall control layers respectively and also have its middle portion directly stacked on the underlying layer.
When the free magnetic layer is directly stacked on the magnetic domain-wall control layers, switched connection occurs in a large area therebetween to effectively inhibit the movement of the magnetic domain wall of the free magnetic layer, and further, when the free magnetic later is directly stacked on the underlying layer, the free magnetic layer is improved in crystallinity, which in turn improves the soft magnetism properties. So far, however, there is provided no magnetic head having such a construction that satisfies both requirements of the free magnetic layer that effective inhibiting of the magnetic domain wall movement and improvement in the soft magnetism properties.
Since in the above-mentioned magneto-resistance effect type head, the free magnetic layer is formed in such a manner as to have its both ends directly stacked on one pair of the magnetic domain-wall control layers and have its middle portion directly stacked on the underlying layer, the movement of the magnetic domain wall of the free magnetic layer at both ends of thereof can be effectively inhibited to thereby suppress the occurrence of the Barkhausen noise in a stable manner, and further, improved soft magnetism properties can be obtained at the middle portion of the free magnetic layer to thereby detect the intensity of the magnetic field with a high sensitivity.
Furthermore, if switched connection thus occurs, the magnetic domain-wall control layer can be thinned without generating the Barkhausen noise, thus qualifying the magneto-resistance effect type head for use in the reproduction of information recorded at a high recording density on a magnetic disk.
Preferably the first magneto-resistance effect type head of the present invention has the underlying layer made of Ta.
Since the underlying layer is made of Ta, the free magnetic layer directly stacked on the underlying layer can have especially good crystallinity and so good soft magnetism properties and, moreover, a current through the above-mentioned magneto-resistance effect element is little shunted to the underlying layer made of Ta having a large specific resistance and so effectively flows to this magneto-resistance effect element, thus permitting this magneto-resistance effect type head to detect the intensity of the magnetic field at a particularly high sensitivity.
To the above-mentioned end, a second magneto-resistance effect type head according to the present invention includes:
a magneto-resistance effect element exhibiting a change in resistance in correspondence with an intensity of an external magnetic field, to detect the magnitude of the resistance of the magneto-resistance effect element, thus detecting the intensity of the magnetic field, in such a configuration that:
the magneto-resistance effect element is comprised of a multi-layer film including a free magnetic layer which has a magnetization direction changing in correspondence with the external magnetic field, the magneto-resistance effect type head having:
an insulating layer made of an insulating material;
a non-magnetic underlying layer formed on the insulating layer;
one pair of electrodes formed on the underlying layer in its in-face direction with a predetermined spacing therebetween, for flowing a current to the magneto-resistance effect element; and
one pair of magnetic domain-wall control layers stacked on one pair of the electrode respectively on the underlying layer in its in-face direction with a predetermined spacing therebetween, for controlling the movement of the magnetic domain wall of the free magnetic layer,
in which the free magnetic layer is formed in such a manner as to have its both ends directly stacked on the pair of the magnetic domain-wall control layers respectively and also have its middle portion directly stacked on the underlying layer.
Since the free magnetic layer is formed in such a manner as to have its both ends directly stacked on one pair of the magnetic domain-wall control layers and have its middle portion directly stacked on the underlying layer, like the above-mentioned first magneto-resistance effect type head, this magneto-resistance effect type head can detect the magnetic field with a high sensitivity while inhibiting occurrence of the Barkhausen noise in a stable manner, thus qualifying itself for use as a head for reproducing information recorded at a high recording density on a magnetic disk.
Further, in the construction that one pair of the magnetic domain-wall control layers are stacked on one pair of the electrode respectively on the underlying layer, the electrodes and the magnetic domain-wall control layers are formed at a high alignment accuracy by a self-alignment method, so that from this viewpoint of a high alignment accuracy in formation besides the above-mentioned thinning of the magnetic domain-wall control layers this magnetic head is suitable for reproducing the information recorded at a high recording density on a magnetic disk. Moreover, no contaminated layer is produced between the electrode and the magnetic domain-wall control layer thus formed by the self-alignment method and, a contaminated layer, if any, between the magnetic domain-wall control layer and the free magnetic layer can be eliminated by cleaning the surface of the magnetic domain-wall control layer. Since there is no such interposition of contaminated layer, the resistance between the electrode and the free magnetic layer can be reduced to easily flow a current therebetween, thus permitting this magneto-resistance effect type head to detect a magnetic field with a high sensitivity.
Preferably the second magneto-resistance effect type head of the present invention has the underlying layer made of Ta.
Since the underlying layer is made of Ta, this magneto-resistance effect type head can detect an intensity of a magnetic field with an especially high sensitivity like the first magneto-resistance effect type head likewise having the underlying layer made of Ta.
Furthermore, in the second magneto-resistance effect type head of the present invention has the above-mentioned electrode, preferably the above-mentioned electrode is made of at least one layer, having a layer made of Ta as its top layer.
Since the electrode has a Ta-made layer at its top in layer, the above-mentioned magnetic domain-wall control layer is formed on this Ta-made layer to improve the crystallinity of this magnetic domain-wall control layer, so that magnetization of the magnetic domain-wall control layer is deflected in the in-face direction of the magnetic domain-wall control layer, thus enabling further effective control on the magnetic domain wall of the free magnetic layer. The magnetic domain wall can thus be conducted effectively, to permit more stable inhibition of occurrence of the Barkhausen noise at this magneto-resistance effect type head.
Furthermore, preferably the second magneto-resistance effect type head of the present invention has the above-mentioned magnetic domain-wall control layer provided with a hard magnetic layer made of a CoPt-based alloy.
Generally, CoPt-based alloys have magnetic anisotropy and a high coersive force. The above-mentioned magnetic domain-wall control layer includes the hard magnetic layer made of a CoPt-based alloy and so has a strong static magnetic field on the free magnetic layer to thereby control the magnetic domain wall of the free magnetic layer by switched connection with the free magnetic layer, thus enabling further stable inhibition of occurrence of the Barkhausen noise at this magneto-resistance effect type head.
To the above-mentioned end, a first information reproducing apparatus according to the present invention includes:
a magnetic head arranged in contact or in near contact with a magnetic recording medium in which information is recorded by magnetization, for detecting magnetization at each point on the magnetic recording medium, to reproduce information corresponding to the magnetization detected at each point of the magnetic recording medium by the magnetic head, in such a configuration that:
the magnetic head is provided with a magneto-resistance effect element exhibiting a change in resistance in correspondence with an intensity of an external magnetic field comprised of a multi-layer film including a free magnetic layer having a magnetization direction changing in correspondence with the external magnetic field, so that the magnitude of the resistance of the magneto-resistance effect element can be detected to thereby detect the intensity of the magnetic field, the magnetic head having:
an insulating layer made of an insulating material;
a non-magnetic underlying layer formed on the insulating layer; and
one pair of magnetic domain-wall control layers stacked on the underlying layer in its in-face direction with a predetermined spacing therebetween, for controlling the movement of the magnetic domain wall of the free magnetic layer,
in which the free magnetic layer is formed in such a manner as to have its both ends directly stacked on the pair of the magnetic domain-wall control layers respectively and also have its middle portion directly stacked on the underlying layer.
Since in this information reproducing apparatus the magnetic head has the same construction as that of the above-mentioned first magneto-resistance effect type head, it can likewise detect an intensity of the magnetic field with a high sensitivity while inhibiting occurrence of the Barkhausen noise in a stable manner, thus qualifying this reproducing apparatus for use in reproducing the information recorded with a high recording density.
To the above-mentioned end, a second information reproducing apparatus according to the present invention includes:
a magnetic head arranged in contact or in near contact with a magnetic recording medium in which information is recorded by magnetization, for detecting magnetization at each point on the magnetic recording medium, to reproduce information corresponding to the magnetization detected at each point of the magnetic recording medium by the magnetic head, in such a configuration that:
the magnetic head is provided with a magneto-resistance effect element exhibiting a change in resistance in correspondence with an intensity of an external magnetic field comprised of a multi-layer film including a free magnetic layer having a magnetization direction changing in correspondence with the external magnetic field, so that the magnitude of the resistance of the magneto-resistance effect element can be detected to thereby detect the intensity of the magnetic field, the magnetic head having:
an insulating layer made of an insulating material;
a non-magnetic underlying layer formed on the insulating layer;
one pair of electrodes formed on the underlying layer in its in-face direction with a predetermined spacing therebetween, for flowing a current to the magneto-resistance effect element; and
one pair of magnetic domain-wall control layers stacked on one pair of the electrodes respectively on the underlying layer in its in-face direction with a predetermined spacing therebetween, for controlling the movement of the magnetic domain wall of the free magnetic layer,
in which the free magnetic layer is formed in such a manner as to have its both ends directly stacked on the pair of the magnetic domain-wall control layers respectively and also have its middle portion directly stacked on the underlying layer.
Since in this information reproducing apparatus the magnetic head has the same construction as that of the above-mentioned second magneto-resistance effect type head, it can likewise detect an intensity of the magnetic field with a high sensitivity while inhibiting occurrence of the Barkhausen noise in a stable manner, thus qualifying this reproducing apparatus for use in reproducing the information recorded with a high recording density.
As described above, the present invention provides a magneto-resistance effect type head and an information reproducing apparatus which can properly reproduce information recorded at a high recording density on a recording medium with a high sensitivity while inhibiting the occurrence of the Barkhausen noise.